A passive optical network (PON) is a point-to-multipoint, fiber to the premises optical distribution network architecture in which unpowered optical splitters are used to enable a single optical fiber to serve multiple premises, typically 16-128. A PON consists of an optical line terminal (OLT) at the service provider's central office and a number of optical network terminals (ONT) or optical network units (ONUs) near end users. A PON reduces the amount of fiber and central office equipment required compared with point to point architectures.
In a PON, downstream signals are broadcasted to all premises sharing multiple fibers. Encryption is used to prevent eavesdropping. Upstream signals are combined using a multiple access protocol, usually time division multiple access (TDMA). The OLT may range the ONUs in order to provide time slot assignments for upstream communication.
In communication systems, a receiver is disposed to detect an input signal where the input signal often has signal levels with varying amplitude. For example, signals transmitted in a passive optical network (PON) often have signal levels with widely varying amplitude. It is sometimes necessary for the receiver to make a determination of the presence or absence of a signal at the input and to provide an indication thereof.